Neosporosis is a parasitic disease caused by a protozoon Neospora caninum, which is recognized as an important cause of bovine abortion and canine neuropathy. Considering the isolation of N. caninum and the frequent serology in bovines of our region, the objectives of the present trial were to evaluate the occurrence of antibodies anti-N. caninum in dogs of the Botucatu range micro region, in the State of São Paulo, and its association with gender, age and origin (urban area--exclusively from the city; rural area--only farms and cottages; and periurban area--access to the urban and rural areas) of the dogs studied. A total of 963 dogs of defined breeds or non-defined breeds, of both genders and different ages, showing no clinical symptoms, were analyzed. Animals were randomly selected during the anti-rabies vaccination campaign in the region, from May to September 1998. Serum samples obtained from the animals were evaluated by means of the Indirect Fluorescent Antibody Test (IFAT) using as antigen N. caninum, standard strain NC-1. A total of 245 animals were reagent (25.4% positive results), with 161 (27.5%) males and 84 (22.3%) females. According to the origin--urban, rural and periurban areas--223 (25.8%), 11(16.9%) and 11(33.3%) dogs were, respectively, reagent to the IFAT. All of the 11 cities in this region presented seropositive dogs with occurrence rates ranging from 53.5 to 8.9%. The lower positive percentage was observed in dogs below 1 year old (16.2%) when compared with animals from 1 to 4 years old and more than 4 years old (28.4% and 28.0% respectively), which did not present any differences between them. Results obtained characterized the seropositivity for N. caninum in dogs from all Municipalities in the Botucatu micro region showing the wide distribution of the agent in the region.